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Python Variables

Last Updated : 22 Apr, 2026

Variables are used to store data that can be referenced and manipulated during program execution. A variable is essentially a name that is assigned to a value.

  • Unlike Java and many other languages, Python variables do not require explicit declaration of type.
  • Type of the variable is inferred based on the value assigned.
Python 
x = 5
name = "Samantha"  
print(x)
print(name)

Output
5
Samantha

Rules for Naming Variables

To use variables effectively, we must follow Python’s naming rules:

  1. Variable names can only contain letters, digits and underscores (_).
  2. A variable name cannot start with a digit.
  3. Variable names are case-sensitive like myVar and myvar are different.
  4. Avoid using Keywords like if, else, for as variable names.

Below listed variable names are valid:

Python 
age = 21
_colour = "lilac"
total_score = 90

Below listed variables names are invalid:

Python 
1name = "Error"  # Starts with a digit
class = 10       # 'class' is a reserved keyword
user-name = "Doe"  # Contains a hyphen

Assigning Values to Variables

Basic Assignment: Variables are assigned values using the = operator.

Python 
x = 5
y = 3.14
z = "Hi"

Dynamic Typing: variables are dynamically typed, meaning the same variable can hold different types of values during execution.

Python 
x = 10
x = "Now a string"

Multiple Assignments

Assigning Same Value: allows assigning the same value to multiple variables in a single line, which can be useful for initializing variables with the same value.

Python 
a = b = c = 100
print(a, b, c)

Output
100 100 100

Assigning Different Values: we can assign different values to multiple variables simultaneously, making the code concise and easier to read.

Python 
x, y, z = 1, 2.5, "Python"
print(x, y, z)

Output
1 2.5 Python

Concept of Object Reference

Let us assign a variable x to value 5.

x = 5

When x = 5 is executed, Python creates an object to represent the value 5 and makes x reference this object.

1
object reference

Now, let's assign another variable y to the variable x.

y = x

This statement creates y and references the same object as x, not x itself. This is called a Shared Reference, where multiple variables reference the same object.

2
shared reference

Now, if we write

x = 'Geeks'

Python creates a new object for the value "Geeks" and makes x reference this new object.

3
shared reference example

The variable y remains unchanged, still referencing the original object 5. Now, If we assign a new value to y:

y = "Computer"

4
shared reference example
  • Python creates yet another object for "Computer" and updates y to reference it.
  • The original object 5 no longer has any references and becomes eligible for garbage collection.
  • Python variables hold references to objects, not the actual objects themselves.
  • Reassigning a variable does not affect other variables referencing the same object unless explicitly updated.

Understanding Variable Reassignment

In this example, we check whether modifying one variable affects another when both initially reference the same object.

Python 
x = 1
y = x
y = y + 1

print(x)
print(y)

Output
1
2

Explanation:

  • Initially, both x and y reference the same object 1
  • When y = y + 1 is executed, python creates a new object 2
  • y now references this new object and x still references the original object 1
  • So, changing y does NOT affect x

Type and Casting a Variable

  • Type of a variable can be determine using type() function which returns the type of the object passed to it.
  • Type casting means converting the value of one data type into another. Python provides several built-in functions to facilitate casting, including int(), float() and str() among others.
  • For example, int() converts compatible values to an integer, float() to a floating point number and str() to a string.

Deleting a Variable

We can remove a variable from the namespace using the del keyword. This deletes the variable and frees up the memory it was using.

Python 
x = 10
del x
print(x)

Output

ERROR!
Traceback (most recent call last):
File "<main.py>", line 3, in <module>
NameError: name 'x' is not defined

Explanation:

  • del x removes the variable x from memory.
  • After deletion, trying to access the variable x results in a NameError indicating that the variable no longer exists.

Practical Examples

1. Swapping Two Variables: Using multiple assignments, we can swap the values of two variables without needing a temporary variable.

Python 
a, b = 5, 10
a, b = b, a
print(a, b)

Output
10 5

2. Counting Characters in a String: Assign the results of multiple operations on a string to variables in one line.

Python 
word = "Python"
length = len(word)
print("Length of the word:", length)

Output
Length of the word: 6

Recommended Problems : Type Conversion, TypeCast And Double It, Swap, Sum of N Numbers, Int Str

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